A fracturing device and method based on phase change of liquid carbon dioxide

Abstract

This invention discloses a fracturing device and method based on liquid carbon dioxide phase change, relating to the fields of reservoir stimulation technology in deep geological engineering, hot dry rock geothermal development, tight oil and gas, and coalbed methane extraction. The fracturing device based on liquid carbon dioxide phase change includes an inner tube, an outer tube, a pressure regulating plate, and jet nozzles. The inner tube is placed inside the outer tube, and the pressure regulating plate is located at the pressure relief port of the inner tube. A clearance fit is formed between the inner wall of the outer tube and the outer wall of the inner tube to form an annular pressure-stabilizing cavity surrounding the inner tube. Multiple jet nozzles are arranged circumferentially on the outer tube, and the air inlet of each jet nozzle is connected to the pressure-stabilizing cavity. The jet nozzles output high-pressure fluid jets to break rocks. Before entering each jet nozzle, the high-pressure fluid undergoes pressure equalization in the pressure-stabilizing cavity, ensuring that the fluid pressure at the inlet of the multiple circumferentially arranged jet nozzles on the outer tube tends to be consistent, thereby achieving synchronous and uniform injection from multiple nozzles.

Description

Technical Field

[0001] This invention relates to the field of reservoir stimulation technology in deep geological engineering, hot dry rock geothermal development, tight oil and gas and coalbed methane extraction, and in particular to a fracturing device and fracturing method based on liquid carbon dioxide phase change. Background Technology

[0002] In the development of deep geothermal resources (such as hot dry rock geothermal resources) and the extraction of tight oil and gas and coalbed methane, reservoir rock masses typically possess extremely high density and very high uniaxial compressive strength. In order to establish an artificial fracture network with high conductivity, effective fracturing stimulation of the reservoir must be implemented to open up fluid seepage channels.

[0003] Currently, the following technical methods are mainly used for fracturing stimulation of deep hard rock reservoirs: Firstly, there is the shaped charge perforation projectile technology. This technology utilizes the high-speed metal jet generated by the explosion of explosives to penetrate the casing and near-wellbore rock, forming a perforation channel. However, in the high-temperature and high-pressure environment of deep wells, the explosives in the shaped charge perforation projectile are highly susceptible to premature detonation, posing a serious safety hazard. Simultaneously, the explosive detonation creates a compaction zone around the perforation channel, reducing near-wellbore permeability.

[0004] Secondly, there is the mechanical armor-piercing perforation technology. This technology uses high-pressure gas to drive solid metal rivets or projectiles to impact and penetrate casing and rock at high speed. However, when facing high-strength crystalline bedrock (such as granite and gneiss), the solid projectiles often fail to penetrate the target formation due to insufficient kinetic energy. More seriously, the projectiles are prone to severe deformation during penetration and become stuck in the casing wall or rock, making it impossible to safely retrieve the downhole tool string and causing major engineering accidents.

[0005] Therefore, there is an urgent need to design a fracturing device and method based on the phase change of liquid carbon dioxide to solve the technical problems of insufficient fracturing efficiency and excessive safety hazards in the existing technology. Summary of the Invention

[0006] This invention provides a fracturing device and method based on liquid carbon dioxide phase change, in order to solve the technical problems of insufficient fracturing efficiency and excessive safety hazards in the prior art.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a fracturing device based on liquid carbon dioxide phase change, comprising: Inner tube, outer tube, pressure plate, and jet nozzle; The inner tube is placed inside the outer tube, and the pressure relief plate is located at the pressure relief port of the inner tube and seals the inner tube to form a closed cavity inside the inner tube for containing the liquid carbon dioxide. The inner wall of the outer tube and the outer wall of the inner tube are fitted with a clearance to form an annular pressure-stabilizing cavity surrounding the inner tube. The jet nozzles are provided in multiple ways, and the multiple jet nozzles are circumferentially arranged on the outer tube, and the air inlet end of the jet nozzles is connected to the pressure stabilizing chamber.

[0008] Furthermore, the jet nozzle is a Laval nozzle.

[0009] Furthermore, the outer tube and the inner tube are coaxially arranged.

[0010] Furthermore, the pressure relief port is located at the end of the inner tube, and the pressure regulating plate is used to break open when the pressure in the sealed cavity reaches a preset breaking threshold.

[0011] Furthermore, the axial length of the outer tube is greater than the axial length of the inner tube, so that the pressure relief port is located within the arrangement area of ​​the jet nozzle on the outer tube wall.

[0012] Furthermore, the open end of the outer tube is provided with a sealing disc, and the sealing disc is provided with a limiting groove for installing the inner tube. The end of the inner tube away from the pressure relief port is engaged with the limiting groove.

[0013] Furthermore, the Laval nozzle is provided with a converging section, a critical throat, and a dilating section in sequence along the flow direction; An arc-shaped transition section is provided between the contraction section and the critical throat, and between the expansion section and the critical throat.

[0014] Furthermore, it also includes a detonation assembly disposed within the sealed cavity.

[0015] Furthermore, the jet nozzle is made of tungsten carbide-based hard alloy material.

[0016] A fracturing method using a fracturing device based on liquid carbon dioxide phase change, characterized by comprising the following steps: The inner tube is coaxially inserted into the outer tube, and the pressure relief port of the inner tube is sealed by a pressure regulating plate. Liquid carbon dioxide is then filled into the inner tube to form a closed high-pressure cavity inside the inner tube. The assembled device is lowered to a predetermined depth in the target reservoir; The liquid carbon dioxide in the inner tube is heated to increase its pressure; When the pressure reaches the set breaking threshold of the pressure regulating plate, the pressure regulating plate breaks, and the high-pressure carbon dioxide in the inner tube is instantly released into the annular pressure regulating chamber for pressure stabilization and equalization. After pressure equalization, the high-pressure carbon dioxide enters from the annular pressure stabilizing chamber into multiple jet nozzles arranged circumferentially on the outer tube. It is accelerated and ejected through each jet nozzle to form a high-speed fluid jet, which impacts and fractures the reservoir.

[0017] Compared with the prior art, the technical solution disclosed in this invention has the following beneficial effects: By adopting the above-mentioned scheme, this invention uses high-pressure fluid jets output from jet nozzles to break rocks, abandoning the traditional solid metal rivets or projectile ejection structures. This completely avoids engineering failures such as insufficient projectile kinetic energy preventing penetration of the formation, or deformation and jamming during penetration leading to the inability to safely retrieve the downhole tool string, significantly improving the reliability of downhole operations. Furthermore, before entering each jet nozzle, the high-pressure fluid undergoes pressure equalization in a pressure stabilizing chamber, ensuring that the fluid pressure at the inlet of the multiple jet nozzles arranged circumferentially on the outer pipe tends to be consistent. This achieves synchronous and uniform injection from multiple nozzles, avoiding jet energy loss due to uneven pressure distribution and improving the utilization efficiency of high-pressure energy generated by the phase change of liquid carbon dioxide. At the same time, it subjects the surrounding rock mass to uniform fracturing, which is conducive to the formation of a more complex and interconnected fracture network, thereby improving the overall effect of reservoir stimulation. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Fig. 1 This is a schematic diagram of the crack initiation device based on liquid carbon dioxide phase change in an embodiment of the present invention; Fig. 2 This is a schematic diagram of the outer tube structure in an embodiment of the present invention; Fig. 3 This is a schematic diagram of the inner tube structure in an embodiment of the present invention; Fig. 4 This is a schematic diagram of the jet nozzle in an embodiment of the present invention.

[0020] Among them, 1. Inner tube; 2. Outer tube; 3. Pressure plate; 4. Jet nozzle; 41. Contraction section; 42. Critical throat; 43. Expansion section. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] This invention provides a fracturing device and method based on liquid carbon dioxide phase change, in order to solve the technical problems of insufficient fracturing efficiency and excessive safety hazards in the prior art.

[0024] like Figs. 1 to 4 As shown in the embodiment of the present invention, a cracking device based on liquid carbon dioxide phase change includes an inner tube 1, an outer tube 2, a pressure regulating plate 3, and a jet nozzle 4. The inner tube 1 is placed inside the outer tube 2, and the pressure regulating plate 3 is located at the pressure relief port of the inner tube 1 and seals the inner tube 1 to form a closed cavity for containing liquid carbon dioxide inside the inner tube 1. The inner wall of the outer tube 2 and the outer wall of the inner tube 1 are fitted with a clearance to form an annular pressure stabilizing cavity surrounding the inner tube 1. Multiple jet nozzles 4 are provided, and the multiple jet nozzles 4 are circumferentially arranged on the outer tube 2, and the air inlet end of the jet nozzle 4 is connected to the pressure stabilizing cavity.

[0025] When fracturing operations are required, a predetermined mass of liquid carbon dioxide is first injected into the sealed cavity of the inner tube 1 through a surface filling device. Then, the device is lowered to the predetermined depth of the target reservoir. After reaching the predetermined position, the temperature of the liquid carbon dioxide in the inner tube 1 is further increased by heating, and the pressure in the cavity rises sharply. When the pressure reaches the preset breaking threshold of the pressure plate 3, the pressure plate 3 breaks instantly, and the high-pressure liquid carbon dioxide in the inner tube 1 is rapidly released in a very short time and enters the annular pressure stabilizing cavity between the inner tube 1 and the outer tube 2. After the high-pressure fluid completes pressure equalization in the annular pressure stabilizing cavity, it simultaneously enters the multiple jet nozzles 4 arranged circumferentially on the outer tube 2. The jet nozzles 4 accelerate the ejection, forming multiple high-speed fluid jets that impact and fracture the well casing and surrounding rocks.

[0026] It should be emphasized that when liquid carbon dioxide is further heated, its volume can expand rapidly by several to tens of times within milliseconds, generating extremely high pressure in the sealed cavity of the inner tube 1. This high pressure energy is the direct power source that propels the fluid to be accelerated out through the jet nozzle 4.

[0027] Based on this, the present invention uses high-pressure fluid jets output from jet nozzles 4 to break rocks, abandoning the traditional solid metal rivets or projectile ejection structures. Since there are no solid projectiles, it completely avoids engineering failures such as insufficient kinetic energy of the projectiles preventing penetration of the formation, or deformation and jamming during penetration leading to the inability to safely retrieve the downhole tool string, significantly improving the reliability of downhole operations. On this basis, the high-pressure fluid is first pressure-equalized in the pressure stabilizing chamber before entering each jet nozzle 4, ensuring that the fluid pressure at the inlet of the multiple jet nozzles 4 arranged circumferentially on the outer pipe 2 tends to be consistent, thereby achieving synchronous and uniform injection of multiple nozzles, avoiding jet energy loss caused by uneven pressure distribution, and improving the utilization efficiency of high-pressure energy generated by the phase change of liquid carbon dioxide. At the same time, multiple jet nozzles 4 are arranged circumferentially on the outer pipe 2, which can simultaneously carry out jet impact in multiple directions around the wellbore, so that the rock mass around the well is subjected to uniform fracturing, which is conducive to the formation of a more complex and interconnected fracture network, thereby improving the overall effect of reservoir stimulation.

[0028] As a further optimization, the present invention also includes a detonation assembly disposed within a sealed cavity. Specifically, the detonation assembly is disposed inside the sealed cavity of the inner tube 1 and centrally arranged along the axial direction of the inner tube 1, and electrically connected to the ground control system via cable or wireless signal. The detonation assembly is activated upon receiving a detonation command from the ground, heating the liquid carbon dioxide filling the sealed cavity to rapidly increase its temperature, thereby inducing a violent phase change and expansion of the liquid carbon dioxide, causing the pressure within the sealed cavity to rise sharply to the breaking threshold of the pressure plate 3. Preferably, the detonation assembly is a chemically exothermic agent. This chemically exothermic agent is connected to the ground control system via an electric igniter or electric fuse, and upon energization, undergoes an exothermic chemical reaction, releasing a large amount of heat to rapidly heat the liquid carbon dioxide within the sealed cavity. Preferably, the detonation assembly is an electric heating activator, which uses a resistance heating element or an electromagnetic induction heating element, directly converting electrical energy into heat energy upon energization to heat the liquid carbon dioxide within the sealed cavity.

[0029] In this embodiment, the jet nozzle 4 is a Laval nozzle. The Laval nozzle has a contraction-expansion type variable cross-section nozzle structure, comprising a smoothly transitioning contraction section 41, a critical throat, and an expansion section 43 along the fluid flow direction. The inlet end of the contraction section 41 forms the air inlet of the jet nozzle 4 and communicates with the annular pressure-stabilizing chamber; the outlet end of the expansion section 43 forms the air outlet of the jet nozzle 4, facing the outside of the outer pipe 2. Arc-shaped transition sections are provided between the contraction section 41 and the critical throat 42, and between the expansion section 43 and the critical throat 42. When high-pressure liquid carbon dioxide enters the contraction section 41 of the Laval nozzle from the annular pressure-stabilizing chamber, the fluid is gradually compressed and accelerated; when flowing through the critical throat, the fluid velocity reaches the speed of sound; after entering the expansion section 43, the fluid expands rapidly due to pressure release and is further accelerated to a supersonic state, forming a supersonic fluid jet that is ejected from the outlet of the expansion section 43. For those skilled in the art, the ratio of the critical throat diameter to the outlet diameter of the expansion section 43 of the Laval nozzle is designed based on the hydrodynamic matching of the breaking pressure set by the constant pressure plate 3. Preferably, the jet nozzle 4 is preferably made of tungsten carbide-based hard alloy material to meet the usage requirements. Furthermore, the jet nozzle 4 is fixedly connected to the wall of the outer tube 2 by interference fit, threaded connection, or welding. The inlet end face of the jet nozzle 4 is flush with the inner wall surface of the outer tube 2, and the outlet end face of the jet nozzle 4 is flush with or slightly higher than the outer wall surface of the outer tube 2.

[0030] In this embodiment, the outer tube 2 and the inner tube 1 are coaxially arranged, and the pressure relief port is located at the end of the inner tube 1. The pressure regulating plate 3 is used to break open when the pressure in the sealed cavity reaches a preset fracture threshold. An annular pressure stabilizing cavity with equal gaps is formed between the inner wall of the outer tube 2 and the outer wall of the inner tube 1, ensuring that the circumferential spatial dimensions of the annular pressure stabilizing cavity are uniform. This allows high-pressure carbon dioxide, after being ejected from the pressure relief port of the inner tube 1, to diffuse uniformly within the annular pressure stabilizing cavity and quickly achieve circumferential pressure equilibrium. As a further optimization, in this embodiment, multiple jet nozzles 4 are uniformly arranged along the circumference of the outer tube 2 and also uniformly distributed along the axial direction of the outer tube 2. That is, the circumferential angle between any two adjacent jet nozzles 4 is equal, and the axial distance between any two adjacent jet nozzles 4 is equal. Furthermore, the outlet direction of each jet nozzle 4 is towards the radial direction of the outer tube 2. Based on this, the inlet pressure of each nozzle can be made as uniform as possible, achieving bulk uniform fracturing of the reservoir.

[0031] In this embodiment, the axial length of the outer tube 2 is greater than the axial length of the inner tube 1, so that the pressure relief port is located within the arrangement area of ​​the jet nozzle 4 on the wall of the outer tube 2. Specifically, the two ends of the outer tube 2 extend beyond the two ends of the inner tube 1 by a predetermined length, the inner tube 1 is completely contained inside the outer tube 2, the pressure relief port is set at the axial end of the inner tube 1, the jet nozzle 4 is arranged on the wall of the outer tube 2, and the arrangement area of ​​the jet nozzle 4 covers the location of the pressure relief port in the axial direction, so that the pressure relief port does not exceed the arrangement range of the jet nozzle 4 in the axial direction, so that the high pressure fluid directly enters the pressure stabilizing chamber for pressure stabilization after being discharged from the pressure relief port.

[0032] In this embodiment, a sealing disc is provided at the open end of the outer tube 2. The sealing disc has a limiting groove for installing the inner tube 1. The end of the inner tube 1 away from the pressure relief port is engaged with the limiting groove to achieve axial positioning and radial limiting of the inner tube 1 inside the outer tube 2. Preferably, the sealing disc is fixed to the open end of the outer tube 2 by a threaded connection or a flange connection, and a sealing ring is provided to achieve end sealing. Preferably, the limiting groove is an annular groove or a circular countersunk hole, and the inner tube 1 is correspondingly provided with an annular boss or a cylindrical protrusion, which is inserted into the limiting groove to form a snap-fit ​​fit.

[0033] This invention also discloses a fracturing method using a fracturing device based on liquid carbon dioxide phase change, comprising the following steps: The inner tube 1 is coaxially inserted into the outer tube 2. The pressure relief port of the inner tube 1 is sealed by the pressure plate 3. Liquid carbon dioxide is filled into the inner tube 1 to form a closed high-pressure cavity inside the inner tube 1. The assembled device is lowered to a predetermined depth in the target reservoir; The liquid carbon dioxide in inner tube 1 is heated to increase its pressure; When the pressure reaches the set breaking threshold of the pressure regulating plate 3, the pressure regulating plate 3 breaks, and the high-pressure carbon dioxide in the inner tube 1 is instantly released into the annular pressure regulating chamber for pressure stabilization and equalization. After pressure equalization, the high-pressure carbon dioxide enters from the annular pressure stabilizing chamber into multiple jet nozzles 4 arranged circumferentially in the outer tube 2. It is accelerated and ejected through each jet nozzle 4 to form a high-speed fluid jet, which impacts and fractures the reservoir.

[0034] Taking the perforation enhancement and production increase of a deep granite geothermal well as an example: Step 1: Wellhead Surface Assembly and Target Parameter Setting. During the construction preparation phase, the in-situ stress and uniaxial compressive strength of the target granite reservoir are obtained based on previous logging data. The maximum required blasting load is then calculated backwards from this data. To ensure that the liquid carbon dioxide jet can effectively overcome the in-situ formation stress and initiate fracturing, the minimum fracturing pressure required by the device (i.e., the design shear fracturing threshold of pressure plate 3) is calculated backwards based on the thick-walled cylindrical elastic-compression fracturing criterion. The in-situ stress fracturing pressure P of the target granite reservoir... fThe calculation formula is: P f =3σ h -σ H +S t -P p In the formula: σ h σ represents the minimum horizontal principal stress of the target reservoir obtained from well logging data, in MPa. H The maximum horizontal principal stress of the target reservoir is expressed in MPa; S t P represents the uniaxial tensile strength of crystalline bedrock (granite), expressed in MPa. p This represents the original pore pressure of the formation, expressed in MPa.

[0035] To ensure that the supersonic jet retains sufficient kinetic energy and static pressure to generate a strong gas wedge fracturing effect after penetrating the casing and cement ring, the burst release threshold P0 of the constant pressure plate 3 must meet the design requirements of the kinetic energy compensation coefficient, namely: P0=K P f In the formula, K is the safety factor for jet penetration and kinetic energy compensation, and its value is usually between 1.2 and 1.5. Based on the above calculation process and the high stress and high strength characteristics of deep granite, the shear fracture threshold P0 of the constant pressure plate 3 calculated in reverse in this embodiment is set to 350 MPa.

[0036] Select an inner tube 1 with an inner diameter of 47mm and fit it inside the outer tube 2 and fix it. Use a ground filling device to precisely fill the inner tube 1 with a specific mass of liquid carbon dioxide. Then, assemble a pressure plate 3 with a shear fracture threshold of 350MPa and an initiation assembly according to the formation strength. After that, inject inert gas into the pressure stabilizing chamber. Finally, use a sealing plate to seal the outer tube 2. The inert gas plays a role in heat insulation.

[0037] Step Two: The assembled fracturing device based on liquid carbon dioxide phase change is lowered into the target section of the granite reservoir at a depth of 3000m-4000m via coiled tubing or high-strength drill pipe, and the depth and perforation azimuth are locked. During the deep well lowering process, the formation temperature is typically as high as 150-200℃. The pre-reserved flow stabilization cavity between the inner and outer tubes 2, as well as the inert gas inside, provides thermal insulation, preventing the liquid carbon dioxide in the inner tube 1 from undergoing premature phase change expansion due to deep geothermal radiation, thus ensuring the safety of the device during the well lowering process.

[0038] Step 3: After the lower section is in position, the ground control vehicle issues a detonation command to the downhole cable, activating the detonation assembly in inner tube 1. When the pressure inside the cavity exceeds the 350MPa threshold, the pressure regulating plate 3 is instantly sheared and torn apart, and high-pressure fluid rushes into the flow stabilization chamber.

[0039] Step 4: The high-pressure fluid in the stabilizing chamber is forced into each jet nozzle 4 at high speed. The fluid accelerates to the speed of sound in the contraction section 41. After passing through the critical throat and entering the expansion section 43, it expands rapidly due to pressure release and is further accelerated to a supersonic state, completing the initial fixed-point perforation of pure fluid. After the jet kinetic energy is exhausted, it is converted into extremely high static pressure, which becomes a fluid "gas wedge" that drills into the depths of the original micro-fractures in the rock. With the advantage of extremely low viscosity, the high-pressure fluid overcomes the deep triaxial geostress, forcing the granite to undergo strong tensile and shear fractures.

[0040] Step 5: Equipment recycling.

[0041] It should be noted that, for those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A fracturing device based on liquid carbon dioxide phase change, characterized in that, include: Inner tube, outer tube, pressure plate, and jet nozzle; The inner tube is placed inside the outer tube, and the pressure relief plate is located at the pressure relief port of the inner tube and seals the inner tube to form a closed cavity inside the inner tube for containing the liquid carbon dioxide. The inner wall of the outer tube and the outer wall of the inner tube are fitted with a clearance to form an annular pressure-stabilizing cavity surrounding the inner tube. The jet nozzles are provided in multiple ways, and the multiple jet nozzles are circumferentially arranged on the outer tube, and the air inlet end of the jet nozzles is connected to the pressure stabilizing chamber.

2. The fracturing device based on liquid carbon dioxide phase change according to claim 1, characterized in that, The jet nozzle is a Laval nozzle.

3. The fracturing device based on liquid carbon dioxide phase change according to claim 1, characterized in that, The outer tube and the inner tube are coaxially arranged.

4. The fracturing device based on liquid carbon dioxide phase change according to claim 3, characterized in that, The pressure relief port is located at the end of the inner tube, and the pressure regulating plate is used to break and open when the pressure in the sealed cavity reaches a preset breaking threshold.

5. The fracturing device based on liquid carbon dioxide phase change according to claim 4, characterized in that, The axial length of the outer tube is greater than the axial length of the inner tube, so that the pressure relief port is located within the arrangement area of ​​the jet nozzle on the outer tube wall.

6. The fracturing device based on liquid carbon dioxide phase change according to claim 5, characterized in that, The outer tube has a sealing plate at its open end, and the sealing plate has a limiting groove for installing the inner tube. The end of the inner tube away from the pressure relief port is engaged with the limiting groove.

7. The fracturing device based on liquid carbon dioxide phase change according to claim 2, characterized in that, The Laval nozzle is provided with a converging section, a critical throat, and a dilating section in sequence along the flow direction; An arc-shaped transition section is provided between the contraction section and the critical throat, and between the expansion section and the critical throat.

8. The fracturing device based on liquid carbon dioxide phase change according to claim 1, characterized in that, It also includes a detonation assembly disposed within the sealed cavity.

9. The fracturing device based on liquid carbon dioxide phase change according to claim 1, characterized in that, The jet nozzle is made of tungsten carbide-based cemented carbide material.

10. A fracturing method using the fracturing device based on liquid carbon dioxide phase change as described in any one of claims 1-9, characterized in that, Includes the following steps: The inner tube is coaxially inserted into the outer tube, and the pressure relief port of the inner tube is sealed by a pressure regulating plate. Liquid carbon dioxide is then filled into the inner tube to form a closed high-pressure cavity inside the inner tube. The assembled device is lowered to a predetermined depth in the target reservoir; The liquid carbon dioxide in the inner tube is heated to increase its pressure; When the pressure reaches the set breaking threshold of the pressure regulating plate, the pressure regulating plate breaks, and the high-pressure carbon dioxide in the inner tube is instantly released into the annular pressure regulating chamber for pressure stabilization and equalization. After pressure equalization, the high-pressure carbon dioxide enters from the annular pressure stabilizing chamber into multiple jet nozzles arranged circumferentially on the outer tube. It is accelerated and ejected through each jet nozzle to form a high-speed fluid jet, which impacts and fractures the reservoir.

Images